Most complex nanoparticle crystal created


Rebecca Pool

Tuesday, March 7, 2017 - 21:00
Image: Gold nanoparticle bipyramids assembled into a complex structure, known as a clathrate, [Glotzer Group].
Researchers from US-based Northwestern University and the University of Michigan claim to have designed and built the most complex crystals ever using DNA and gold nanoparticles.
Professor Chad Mirkin from Northwestern joined forces with Professor Sharon Glotzer from U-M to assemble bipyramidal gold nanoparticles functionalised with DNA molecules into polyhedral clusters, creating open pore structures.
These clusters, composed of up to 42 particles, formed larger polyhedral and connected into cage-like crystal structures called clathrates.
STEM, in Z-contrast mode, and SEM revealed at least three different structures formed as large single-domain architectures or as multidomain materials.
The most complex crystal designed and built from nanoparticles. Left: An electron microscope image of a slice of the structure (Northwestern University). Right: A matching slice from a simulation of the structure (University of Michigan).
The researchers went onto identify ordered assemblies, isostructural to clathrates, using molecular simulations and geometric analysis.
Analyses indicated that the structures are the most sophisticated architectures made via such programmable assembly.
And further investigation also showed structure formation depended on the shape of the nanoparticle building blocks and mode of DNA functionalization.
Electron  microscopy of crystal surface [Mirkin Group].
“This is a tour de force demonstration of what is possible when one harnesses the chemistry of DNA and combines it with nanoparticles whose shapes encourage a particular crystal structure,” says Mirkin. “These are stunning; no one has made such structures before."
Clathrates are well known for containing chambers that can house small molecules; the researchers believe the latest structures could be useful for storing, delivering and sensing materials for environmental, medical diagnostic and therapeutic applications. 
Research is published in Science.
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